Because of their height above ground and the gridwork of support members that carry the display panels, outdoor advertising billboards or signs are a favorite nesting site for birds. Such billboards are sometimes erected in places, such as a parking lot, where human activity takes place underneath the billboard. In those cases, a problem arises from the fact that droppings from the birds nesting on the billboard soil the ground, and objects, such as cars, under the billboard.
Various methods have been used in the past to deter birds from nesting on billboards. These include studding the billboard with sharp spikes such as nails, or placing onto the top surface some propeller-like devices which turn in the wind and scare the birds. Unfortunately, none of these methods have been fully successful, and the droppings problem still persists.